Measuring the Rate Constant for Vitamin B_1 Decomposition Using a Handmade Fluorometer and its Application to Science Teaching

Abstract

In this paper, a developed experimental education material to measure the rate of a chemical reaction is described. Vitamin B_1 (thiamine) is familiar to students as a nutrient. It is oxidized by potassium ferricyanide in alkaline solutions to thiochrome, which exhibits a brilliant blue fluorescence. When thiamine is decomposed in an alkaline solution, the rate of the reaction is proportional to the concentration of thiamine. This is called a first-order reaction. Thiamine has the potential to be a superb educational material to study reaction rates. The rate constant and activation energy for thiamine decomposition can be measured by a handmade fluorometer, which is made of inexpensive materials. The results show that the rate constant k is 0.0085s^<-1>(16.9℃), 0.0167s^<-1>(25.1℃) and the activation energy Ea is 61.5kJmol^<-1>. This new experimental material was introduced in a senior high school science class. Most of the students measured and computed similar figures to the above results. The students were highly motivated and most gave positive answers in the questionnaire.